(i) Field of the Invention
The present invention relates to an ink volatilization preventing composition for an aqueous ball point pen. More specifically, it relates to an ink volatilization preventing composition which prevents the volatilization of an ink in an aqueous ball point pen having an ink tank capable of directly accommodating the ink and which achieves the shelf stability of the ink.
(ii) Description of the Related Art
Heretofore, in a ball point pen having an ink tank into which an ink is directly filled, a back-flow preventer has been put onto the upper surface of the ink in the ink tank in order to prevent the back-flow of the ink. Japanese Patent Laid-open No. 57-153070 discloses such a back-flow preventer, for example, a composition comprising dibenzylidene sorbitol and ethylene glycol, and in Japanese Patent Laid-open No. 57-200472, there is disclosed a composition obtained by dissolving an amino acid derivative in a nonvolatile organic liquid such as vaseline, followed by gelation.
Furthermore, in Japanese Patent Laid-open Nos. 61-57673, 61-145267, 61-151289, 61-200187, 61-268786, 62-50379 and 60-148581, there are disclosed compositions obtained by adding polyoxyethylenesorbitan monolaurate, glycerin dioleate, sorbitan monooleate, pentaerythritol stearate, polyethylene glycol diisostearate, N-oxyethylamine and polyoxyethylene curing castor oil to polybutene and silica.
In general, the ink back-flow preventer in the ink tank is required to follow the movement of the ink owing to the properties of the preventer. However, in the case of the aqueous ball point pen, an ink consumption is about 0.1 g to 0.2 g per 100 m of writing, and this consumption is very large in view of a fact that in the case of an oil ball point pen having a similar structure, the ink consumption is about 0.01 g to 0.04 g per 100 m of writing. In consequence, the aqueous ball point pen consumes the ink rapidly. In the case that the ink is quickly consumed, it seems that the ink back-flow preventer does not adhere to the ink tank, but in fact, the preventer adheres to the inside wall of the ink tank in the state of a film, and when the consumption of the aqueous ball point ink proceeds, the ink back-flow preventer which remains on the upper surface of the ink is surely reduced.
Owing to such a problem, there is a drawback that the conventional ink preventer must be filled as much as about 5% to 20% of the ink tank.